This invention relates to a method of removing residue from an interior of a process chamber, and more particularly, to a method of using environmentally friendly gases to remove unwanted deposits from a process chamber for making electronic devices.
In the electronics industry, vacuum processes chambers are frequently used for making electronic devices. Unused reagents and byproducts of deposition or etch processes are usually exhausted from the chamber, but not residues deposited on the walls and other surfaces inside the chamber. Residues comprising substances like silicone, silicone oxide, silicone nitride and/or tungsten are formed during a process of fabricating semiconductor layers for electronic devices, for example, during fabricating thin film transistor (TFT) flat panel displays, microelectromechanical systems (MEMS), as well as during processes for chemical vapor deposition (CVD) of a film. To maintain quality and consistency of electronic devices being fabricated, these residues have to be removed from the surfaces on which they are coated to prevent them from flaking-off and contaminating the electronic device itself. Many of the prior art methods and processes use perfluoro compounds (PFCs), such as SF6, in plasma etching or reactive ion etching (RIE) thin films and cleaning plasma enhanced CVD chambers. A conventional method of cleaning unwanted residue is to introduce to a process chamber a gas containing radicals produced by plasma decomposition of PFCs, such as SF6 or a mixture thereof with oxygen, argon or chloride.
However, the use of PFCs such as SF6 is extremely damaging to the environment. PFCs and, in particular, SF6 cause an irreversible atmospheric impact because they have extremely long atmospheric lifetimes (thousands of years) and high global warming potential values (GWP100). International concern over global warming has focused attention on the long atmospheric life of SF6 (about 3,200 years, compared to 50-200 years for CO2) together with its high potency as a greenhouse gas (23,900 times the 100-year global warming potential (GWP100) of CO2 on a mole basis) and has resulted in a call for voluntary reductions in emissions. Because of this concern, the use of SF6 is being restricted, and it is expected to be banned in the near future.
Prior art methods of cleaning a semiconductor processing chamber using SF6 include the steps of removal of products of SF6 decomposition such as SO2F2, as disclosed in WO 02/07194 A2 to Ohno et al. Ohno discloses the method of cleaning using a combination of SF6 with either F2 or NF3, wherein the decomposition or reaction products of these gases are removed in a decomposition step after the cleaning.
The U.S. Pat. No. 5,376,234 to Yanagida discloses a dry etching method for etching a silicon layer using an etching gas containing a fluorocarbon compound and, optionally, a halogen compound containing a sulfuryl group.
Other prior art methods of dealing with reducing or eliminating the release of global warming compounds include using molecular fluorine gas (F2) as described by EP 1 138 802 A2 to Harshbarger et al. or carbonfluorides as described by the U.S. Pat. No. 6,242,359 B1to Misra.
However, molecular fluorine and carbonfluorides are relatively expensive and not very environmentally friendly. Fluorine systems require enhanced safety measures due to the reactivity of fluorine. This includes extensive cleaning and pre-passivation of the entire fluorine system.
Despite the foregoing developments, it is still desired to provide other cleaning gases with lower global warming potentials that can be easily decomposed after cleaning. It is further desired to have a process for plasma cleaning which overcomes the disadvantages of the prior art by reducing or eliminating the release of global warming compounds into the atmosphere.
All references cited herein are incorporated herein by reference in their entireties.